Construction of Chitosan/Graphene Oxide Hybrid Hydrogel Electrode with Conductive Porous Network for High Energy Density Flexible Supercapacitor

Abstract

The hybrid hydrogel (MCHG) with conductive porous network and heteratomic functional groups are constructed through microwave-assisted hydrothermal, by cross-linking of modified chitosan (M-chitosan) and holey graphene oxide (HGO). Amides and carboxyl groups are introduced during the acylation modification, enabling M-chitosan soluble in water for sufficient reaction. The oxidation etching occurred for graphene oxide in the defect area of substrate by H2O2 provides MCHG with in-plane nanopores, which can provide abundant active surface and short ion diffusion pathway. Due to the high conductivity and flexibility, MCHG can be used as additive-free electrode in three-electrode and it delivers a high specific capacitance of 377 F/g at 5 A/g. The abundant nitrogen and oxygen groups on surface of MCHG can contribute to high capacitance directly. The in-plane nanopores and hierarchically porous network of MCHG is beneficial to improve their wettability, accelerate the charge transfer and enhance their ability of charge storage. When MCHG is adopted into a flexible solid-state supercapacitor using lignin hydrogel electrolyte, it delivers a specific capacitance of 420 F/g at 0.5 A/g, with ultrahigh energy density of 14.8 Wh/kg at the power density of 100 W/kg. The solid-state supercapacitor exhibits promising potential applications in signal sensors and portable energy storage.

Keywords: modified chitosan, flexible electrode, ultrahigh energy density